The present invention relates generally to vehicle tracking systems, and in particular, to a tracking system for mobile trailers that maintains location and tractor coupling information for a fleet of mobile trailers.
Transportation of cargo via tractor-trailers is an important part of worldwide commerce. (In this context, a xe2x80x9ctractorxe2x80x9d is a reference to a highway truck, such as a semi-truck). The complex and large-scale operations of tractor-trailer fleet owners dictate that the owners keep track of the status and general location of their vehicles as accurately as possible. This facilitates, among other things, efficient allocation of pick-up and delivery of goods, increased equipment utilization, effective maintenance scheduling, improved cargo security, decreased asset losses, and rapid assistance for vehicles in need of repair or help. The advent of the Global Positioning System (xe2x80x9cGPSxe2x80x9d) has greatly assisted these efforts, as geographic location can now be pinpointed within a number of meters, allowing position information for vehicles to be accurately determined. Coupled with a method of reporting a current location for a vehicle, a GPS-based tracking system can provide the kind of centralized tracking and management that fleet owners need, particularly when thousands of vehicles must be tracked.
Numerous systems exist to provide continuous tracking of highway tractors. These tractor-tracking systems include, for example, the xe2x80x9cOmniTRACSxe2x80x9d system from Qualcomm, the Orbcomm data messaging system from Orbcomm company, and the Motient/Norcomm vehicle tracking system. They typically include a GPS system and a satellite-based data messaging system (and, optionally, other sensors and control relays). Messages, including the location of the tractor, are communicated between the tractor and a central office through the satellite-based system. Other systems use cellular-based systems for communications and data messaging. These systems are generally only effective in urban areas or along highways having cellular telephone coverage.
Generally, tractor-tracking systems are not useful or effective for directly tracking mobile trailers. This is because tractor-tracking systems lack any automatic mechanism to identify or monitor trailers, instead requiring an operator to manually input trailer data. As a result, the visibility of a trailer""s location is lost once the trailer is disconnected from the reporting tractor. Additionally, it is not practical to simply install the tractor-tracking systems directly on the mobile trailers. This is because trailers generally only have power when connected to a tractor, and therefore do not have the necessary power source to operate a tractor-tracking system (used here for trailer-tracking) independent of the tractor. It takes a considerable amount of power to communicate with satellites orbiting 22,500 miles above the earth, like the satellites used for Qualcomm""s OmniTracs system.
Some companies do offer untethered trailer-tracking systems, however. (An xe2x80x9cuntetheredxe2x80x9d trailer is a trailer that is not hooked, or does not need to be hooked, to a tractor""s power supply.) For example, Orbcomm""s LEO trailer-tracking system relies upon Low Earth-Orbit satellites for communications. Because LEO satellites are closer to the ground (e.g., 500 miles), less complex and less powerful antennas and communicators can be used to talk to these satellites than with traditional geostationary satellites. Similarly, cellular-based modem systems require less power than traditional satellite-based systems and can be used for untethered trailers, although they lack the coverage of the full-scale tractor-tracking systems. For example, Qualcomm""s TrailerTracs product relies upon a cellular-based system for untethered trailer communication.
Both of these types of untethered trailer-tracking systems rely upon battery power for untethered trailer communications. Their power requirements are substantial. For example, communicating with the Orbcomm LEO satellites consumes power at a rate of almost 6 watts, while a cellular-based modem uses power at a rate of almost 600 mW. At these power levels, batteries can be drained very quickly, limiting the usefulness of such systems. Also, the large power demands placed on the batteries requires that the batteries be serviced often and replaced frequently, and makes the batteries particularly susceptible to failure. These types of systems generally do not communicate with the tractor itself, and therefore cannot provide specific tractor identification and coupling information, other than a basic xe2x80x9ctractor hookedxe2x80x9d determination.
Thus, it would be desirable to provide a trailer-tracking system that can provide automatic tracking of mobile trailers, but without the substantial power requirements of a tractor-based communications system.
Another important issue to tractor-trailer fleet owners is the ability to monitor trailer-yard inventory. When trailers are not in use, they are commonly stored in xe2x80x9ctrailer yards,xe2x80x9d large open facilities with rows of trailers. Large distribution centers may also maintain trailer yards for temporary storage while trailers are being loaded or unloaded. Some trailer yards may contain hundreds, or even thousands, of trailers. An efficient means to keep track of trailers in a yard is very important, for the same reasons that monitoring tractor-trailer fleets is important. Some fleet operators may rely upon the battery-operated untethered trailer-tracking systems to provide GPS position data indicating that a particular trailer is presumed to be in a yard, based on the yard""s known coordinates. Alternatively, some systems provide radio frequency tagging of trailers, known as RFID, or radio frequency ID.
A basic RFID system has three components: (1) an antenna or coil; (2) a transceiver with a decoder; and (3) an RFID tag, also called a transponder, which is electronically programmed with specific information. Transceivers with strategically placed antennas emit radio signals to activate RFID tags. The transceivers can read data from the tag, write data to the tag, or both. Antennas are the link between tags and transceivers, converting between radio waves and electrical signals. Often, antennas are packaged with the transceiver and decoder to become an interrogator, also known as a reader.
RFID tags typically contain an antenna or inductive coil, memory, and a small processor. They can be identified as active or passive, depending on the means by which they obtain their power. Passive tags operate without an internal battery source, deriving their power from the energy transmitted by the reader. A passive tag is energized by radio waves from the reader, and instantaneously transmits a unique pre-coded identifier back to the reader. Active tags utilize a power source such as an internal battery, and therefore reduce the power requirements of the reader. Active tags can provide greater communication range and better noise immunity than passive transponders. Active tags can also result in higher data transmission rates when used at higher radio frequencies.
Interrogators emit radio waves with an effective range of anywhere from one inch to 200 feet or more, depending on the unit""s power output and the radio frequency used. When an RFID tag passes through the interrogation zone, it detects the RF activation signal, causing the tag to transmit its data. The interrogator receives and then decodes the data. Finally, data is passed to the host computer for processing. In the trailer-yard context, RFID tags have been placed on trailers and used to monitor the inventory of trailers in a yard. However, once trailers equipped with RFID tags are outside of the transmit and receive range of the transceiver, visibility for the trailer is lost. Thus it would be desirable to provide a trailer-tracking system that integrates trailer-yard inventorying systems with trailer-position tracking systems.
Thus, a need exists for a system that can track a fleet of mobile trailers, whether tethered or untethered, and whether in transport on a highway or located in a trailer yard.
In one embodiment of the present invention, a position tracking system for a plurality of mobile tractors and trailers includes an unique electronic identifier for each of a plurality of trailers. Also, for each tractor the position tracking system includes a navigation system for determining a current position of the tractor, and an electronic identifier reader for acquiring the electronic identifier of a trailer coupled to the tractor. The position tracking system further includes, for each tractor, a position reporting subsystem that is coupled to the navigation system and to the electronic identifier reader. The position reporting reports to a remote system the current position of the tractor and the electronic identifier of the trailer coupled to the tractor.
In addition, the position tracking system includes, at each facility of a plurality of fixed-location facilities, one or more electronic identifier readers for acquiring the electronic identifier of one or more trailers located within the facility. Each facility also includes a trailer-presence reporting subsystem, coupled to the one or more electronic identifier readers of the facility, for reporting to the remote system the presence of the one or more trailers located within the facility.
Another embodiment of the present invention is a remote system for use with a plurality of mobile tractors, mobile trailers, and fixed-location yards. Each trailer has an unique identifier, which can be read by a tractor to which the trailer is coupled, and that can also be read by a fixed-location yard in which the trailer is located. Further, each tractor has a navigation system for determining a current position of the tractor. The remote system includes a communication module for receiving tractor information, including information identifying a current position of a tractor and an electronic identifier of a trailer coupled to the identified tractor. The tractor information is received from a communication device on the tractor. Additionally, the communication module receives yard information, including an electronic identifier of a trailer located within a fixed-location yard, which is received from a communication device at the fixed-location yard. Further, the remote system includes a database for storing information concerning a location of a subset of each of the plurality of mobile tractors and trailers.
Yet another embodiment of the present invention is a method of maintaining a mobile tractor-tailer database for use in a position tracking system for a plurality of mobile tractors, mobile trailers, and fixed-location yards. Each trailer of the plurality of mobile trailers has an unique identifier that can be read by a tractor to which the trailer is coupled, and that can also be read by a fixed-location yard in which the trailer is located. Further, each tractor has a navigation system for determining a current position of the tractor. The method includes receiving, at a remote system, a report from a communication device on a tractor indicating a current position of the tractor, and indicating an electronic identifier of a first trailer coupled to the tractor. The method further includes receiving, at the remote system, a report from a communication device at a fixed-location facility indicating the electronic identifier of a second trailer present in the facility.
In addition, the method includes storing in the mobile tractor-trailer database at least one entry selected from the group consisting of: (1) a representation of the electronic identifier of the first trailer; (2) an indication that the first trailer is coupled to the tractor; (3) a position, affiliated with the first trailer, representing a current position of the tractor; (4) a representation of the electronic identifier of the second trailer; and (5) an indication that the second trailer is present in the facility.